The present invention relates to a method and apparatus for securing one or more elements or parts, each of which is provided with an opening, to a hollow member, especially cams, bearing rings, and/or drive elements to a hollow shaft. In the starting state, the inner diameter of the opening formed in the parts is greater than the outer diameter of the surface provided on the hollow member for securing said parts. The parts are placed in the prescribed position on the hollow member prior to the securing operation.
It is known in many fields, instead of machining complicated parts from a single solid piece, to produce these parts by securing appropriately shaped supplementary parts to a base member, so that the exterior shape of the component can be produced in the most economical manner. The supplementary parts are secured to the base member by being welded, soldered, shrunk-fit, glued, or otherwise joined thereto. In order to save material and/or weight, hollow members are also frequently used as the base member. In this case also, in the starting state the opening in the part that is to be secured to the hollow member is greater than the securing location of the hollow member, so that the respective part can be placed in the prescribed position on the hollow member prior to starting the securing operation.
In welding and soldering operations, localized thermal stresses occur, especially in the hollow member; these thermal stresses can lead to undesired and difficult-to-control deformations or changes. The drawback of securing the parts by gluing them is that one can never be entirely sure that the contact surfaces are completely wetted or coated with the adhesive.
In the shrink-fit process, the outer diameter of the support location and the inner diameter of the opening in the part that is to be shrunk-fit must be produced with great precision in order to comply with the small tolerances that are required for the desired retention. The difference in diameter achieved by the temperature difference is proportional to the temperature starting point between the components, the temperature coefficients of expansion, and the radii of the components. Since the elastic deformation of the components that are to be interconnected is proportional to the square of the radius, and since the temperature difference that can be achieved in practice is limited, in many cases it is possible to obtain only an unsatisfactory adhesion, especially with certain combinations of materials. Shrunk-fit parts can become loosened, especially when temperature differences due to operation occur in the components.
It is an object of the present invention to provide a method and apparatus of the aforementioned general type, in a simple and economical manner, via which parts ca be reliably secured to a hollow member without the danger of overstressing the hollow member or of a loosening of the parts.